The catalytic hydrogenation reaction using a heterogeneous catalyst, so-called catalytic reductive reaction is one of the most important processes in chemical industry, and is widely utilized for hydrogenation of aromatic nitro compounds and unsaturated bonds or de-benzylation reaction by hydrogenation, but there are often deterioration of yield and slow-down of reaction proceedings. Since these problems are solved by increasing the contact area between each phase, the catalytic surface (solid phase)-solution (liquid phase)-hydrogen gas (gas phase) (hereinafter, to be called a solid-liquid-gas phase reaction or three phase catalytic reduction reaction), such techniques have been tried as vigorous stirring or blowing in hydrogen gas as fine bubbles.
In the catalytic hydrogenation reaction in an ordinary reactor (hereinafter, properly called a flask reaction), ignition or explosion may be possible since hydrogen gas, solvent vapor, and highly active metal catalysts co-exist is the system.
On the other hand, organic syntheses using a micro-reactor have been rapidly developing. A micro-reactor is a generic term for a micro-reactor having micro-channels of the size of several to several hundred μm in an inactive material such as glass. Since a micro-reactor is small, strict temperature control is easily possible. Therefore, synthetic reactions using a micro-reactor have such merits as (1) high reaction efficiency on interfaces, (2) efficient mixing by molecular diffusion, and (3) easy temperature control, owing to large surface area per unit volume.
Thus, since synthetic reactions using a micro-reactor are faster in reaction time than those using ordinary reactors, and use a minute amount of reactants, the cost is low and they have been drawing attention as the reactors to develop novel compounds and medicines.
In Reference 1 in the list shown below, a hydrogenation reaction using a micro-reactor is described, which is a two-phase reaction of gas-solid with a catalyst imreferencemobilized on the inner wall of a micro-channel.
As the methods to pass liquid and gas as reactants through the micro-channels of a micro-reactor, a slug flow and a pipe flow are known. FIG. 8 is a cross-sectional view diagrammatically illustrating (a) slug flow and (b) pipe flow in a conventional micro-channel. As is shown in FIG. 8(a), a slug flow is the state of liquid 52 and gas 53 alternatively passing through a micro-channel 51 provided on a glass substrate. Also, as is shown in FIG. 8(b), as a pipe flow, gas 53 passes in the center part of a micro-channel 51, and liquid 52 passes between the gas 53 and the inner wall 51a of a micro-channel. Which type, a slug or a pipe flow, the fluid in a micro-channel takes can be controlled by adjusting the flow rates of liquid 52 and gas 53 passing through a micro-channel 51.
The reactions by a slug flow in a micro-channel 51 are described in the References listed below. Reference 2 below describes fluorination reaction by a two phase reaction with gas-liquid phases. The reactions by a pipe flow in a micro-channel are mentioned in the References listed below. Reference 3 below describes fluorination reaction by two phase system reaction with gas-liquid phases.
Carbon monoxide insertion reaction is reported as a reaction in a flask (refer to Reference 6.), but there is no reference for carbon monoxide insertion reaction using a micro-channel reactor.
Reference 1: R. S. Besser, and two others, Chem. Eng. Sci., Vol. 58, p. 19 (2003)
Reference 2: K. Jahnisch, et al., J. Fluorine Chem., Vol. 105, p. 117 (2000)
Reference 3: R. D. Chambers and R. C. H. Spink, Chem. Commun. 883 (1999)
Reference 4 M. W. Losey, and two others, Chem. md. Eng. Chem. Res., Vol. 40, p. 2555 (2001)
Reference 5: R. Akiyama and S. Kobayashi, J. Am. Chem. Soc., Vol. 125, pp. 3412 3413 (2003)
Reference 6: J. Kiji, T. Okano, Y. Higashimae, and Y. Fukui, Bull. Chem. Soc. Jpan., Vol. 69, pp. 1029 1031 (1996)
However, such three phase catalytic reactions as three phase catalytic reductive reactions of solid-liquid-gas phases using a heterogeneous catalyst have never so far been effectively realized by a micro-reactor.